Hydraulic fluids



a g 2,736,709 Patented Feb-1 5i: 5

HYDRAULIC. FLUIDS Samuel A. Glickman and Joseph M. Wilkinson, Easton,Pa., assiguors to General Aniline &Fiim Corporation, New York, N. Y., acorporation of. Delaware- No Drawing. Application August 17, M54, SerialNo. 450,512

4.- Claims. (c1. 252-74 This invention relates to hydraulic fluids andparticularly to hydraulic brake fluids containing 3-methoxy-lbutanol and3,5,x-polymethoxy-l alkanolsas the principal ingredients.

Many hydraulic fluid compositions are known to the art. The earliestimproved. fluids contained castor oil and a high boiling diluent inconjunction with various inhibitors. Later modifications included blowncastor oil and castor oil glycol reaction products. However, lowtemperature usefulness, gum formation, and other factors led the art tofind other materials.

When one surveys the field of organic liquids which could possibly besuitable for use as'hydraulic fluidsfrom the standpoint of viscosityat'high and low temperatures, low volatility and lack of corrosiveactionon metals, etc., one is immediately impressed" by the paucity ofcompounds which are acceptable'from-thestandpointof attack or theswelling of rubber. The vast majority'ofotherwise acceptable liquidsincluding esters; ketones', halides, acetals, acids, amines, ethers',hydrocarbons, etc, have far too great a degree of rubber attack. As aresult of many studies, it has been shown that very few organic liquidsare acceptable in this respect. Outstanding among those acceptable arecertain alcohols'and ether alcohols having a favorable oxygentocarbonratio and/ or distribution-in the molecule, i. e'., structuralconfiguration.

To be suitable for use as a hydraulic fluid; a liquid composition musthave the following characteristics: It must not exhibit too great aviscosity change under wide temperature range, i. e., it must bereasonably viscousat the highest temperatures for which use it' iscontemplated, and on the other hand, it must remain fluid'at the lowesttemperatures likely to be encountered in automotive use, e. g., 50 F. Ingeneral, fluids which haveaviscosity of at least 5 cps. at 130 F. and aviscosityno greater than 1500 cps. at 40 F; are considered suitable; Afurther requirement is that the fluid must have a lubricating action onmost parts'of the braking system in order to prevent undesirable wearingduring-use. In this respect, fluids which allow-the moving parts to wearnot more than .001 of an inch during;200,000-braking cycles are usuallyconsidered adequate.

It is an absolute prerequisitethat asuitable fluid should not undulyattack any of the rubber or metal parts in the braking system. Theattack on rubber is so undesirable that extensive research has goneinto=the-manufacture of fluids which show a minimum of swelling orsoftening action on rubber. In regard' to the attack on'the metal parts,it might be saidthat the fluid must have the correct pH value, that is,presumably in the range of 8.5 i to 9.5. In this range, protection wouldbeobtained" against the attack of acid sensitive metals, such as iron,tin,- aluminum, zinc, etc. while this degree of alkalinity is notsufliciently high to cause the attack of alkali sensitive materials,such as aluminum and zinc.

It is a further prerequisite that the fluid: should: have as-loW-avolatility as'is practical to;v achieve,.in:.order. to eliminate thepossibilities of evaporation from the brake system storage unitas wellas topreventthe undesirable evaporation of. the. fluid fromzthe areasadjacent to; hot braking surfaces. In the.past,.tliese: objectionsliavebeen achieved through the use of .various mixtures of? aliphaticalcohols, and glycerine esters, such as castor oil,.soya.oil, etc., orwith mixtures of various ether alcohols, such as fi-butoxy ethanol, themonoethyl ether ofdiethylene glycol and various polymers. ofethylene'oxide, propylene oxide, or. interpolymers. of ethylene andpropylene oxides. The first-mentioned type consisting of alcohols. andnatural oils: has certainshortcomings, eg., with. the lower aliphaticalcohols. The degree of attack on' rubber rapidly increases with. theincreasingchain length of the alcohol used in practice. It has beenfound thatalcohols higher than the butyl alcohols cannotbeused because:of excessive attack on, or'swelling of, the rubber parts? in the brakingsystem. The alcohols up to and i'ncludingthe butyl alcohols have,unfortunately, rather low boiling points and hydraulic brake fluids.prepared with them show an undesirably high degree of volatility.Inaddition,v the presence of natural. glycerine esters, such as castoroil' and/or soyaoil, etc., is undesirable because, as is well known,these substances are subject to oxidation and in time form undesirablegummy materials in. the system. Because of the disadvantages,considerable effort has been, made: to develop improved fluids forhydraulic systems- One composition. which" has been suggested toovercome these disadvantages,- comprises a mixture of theabove-mentionedcomponents: Carbitol, butyl Cellosolve, andfinterpolymersof'etl'rylene oxide and propylene oxide;

While fluids of this typeare better than mixture of alcohols andnatural. oils, they also: have certain. shortcomings; It'has beenestablished that the relatively low boiling points of two of. thecomponents used in such fluids, namely, butyl Cellosolve? and Carbitolfiprevent suchicompositions from". being considered for" high temperatureapplications; It has. been. further established that such compositionswill be prone; to-peroxide formation, a well known:shortcoming.characteristic ofpolyoxyethylenes,. polyox-ypropylenes, and;the various: interpolymers of ethylene.oxidecand-propylene oxide;

We have. founds that the foregoing shortcomings and difliculties' of thepresently utilized fluids, particularly those containingpolyoxyalkylenes' andinterpolymers of alkylene' oxides are substantiallyovercome by'employing an alkaline buffered mixture of- 3-methoxy-1-butanoli and 3,5.x-polymethoxy-l-alkanols': as the principalingredients with or without the presence of minor amounts of auxiliarycomponents, such as' antioxidants, corrosion inhibitors, viscosityregulators, andithelike'.

The 3-methoxy-1-butanol and 3,5-x-polymethoxy-1- alkanols utilizedin themixture are-characterized byv the following general formula:

Where n represents an integer of from 1 to 10.

The alkanols characterized by the foregoing formula are' prepared byreacting, in the known manner, vinyl methyl ether with metha-nol'toyielddimethylacetal and reacting the latter with additional vinyl methylether. The ratio of methanol to vinyl methyl ether may vary from 210:1.0to 20:1, preferably from. 2.0:1 to 5.011, respectively. The crude acetalis then distilled to yield individual components wwhichmaybersubjectedto simultaneous hydrolysis-reduction to yield individual alkoxyalkanolssuch as 3-methoxy-l-butanol; 3,5-dimethoxylhexanol;3,5,7-trimetl1oxy-1.-octanol; 3,5,7,9-tetramethoxy-l-decanol;v3,-5,,7,9,'1l pentamethoxyal:dodecanol. and polymethoxy-l-alkanols. as.described. iii- Examples. 1,. 4, and 5 of United States Patent2,618,663; Alternatively,

the crude acetal may be subjected to simultaneous hydrolysis-reductionas described in Example 3 of said patent and the mixture of alkanolsemployed as such in accordance with the present invention. The mixtureof alkanols may be distilled to yield the individual components of thealkanols and the individual components blended in the ratio of 20 to 40%of 3-methoxy-1-butanol and 60 to 80% of the remaining3,5,x-polymethoxy-lalkanols.

The alkanols are colorless liquids characterized by partial solubilityin water, especially the methoxy derivatives which are completelysoluble in water, and by complete miscibility in organic solvents, suchas aliphatic alcohols, ketones, esters, glycol ethers, aromaticsolvents, and aliphatic petroleum ethers and naphthas. The completemiscibility in aliphatic hydrocarbons is in sharp distinction to thepolyethylene glycols which are virtually insoluble in these solvents.

All of the alkanols in the mixture, i. e., the 3-methoxyl-alkanol and3,5,x-polymethoxy-l-alkanols, when in contact with rubber have a verylow swelling action, considerably less than that tolerated bycommercially available hydraulic fluids. In addition they possess anunusual inertness to oxidation attack. It is believed that thearrangement of atoms in the alkanols of the mixture contributes to thisproperty. This is unexpected since it has been recognized by the art, U.S. P. 2,492,955 and 2,481,278, that polymers of ethylene and propyleneoxide have one serious drawback which limits their use as lubricantsbecause the two carbon unit between the ether linkage in the polymerchain appears to make the polymer extremely sensitive to oxidation.

The hydraulic fluids prepared in accordance with the present inventionpossess sufiicient lubricity under operating conditions in variousclimes and extremes of temperatures. Tests have indicated that thelubricity is met by the presence, even in very small amounts, of thehigher members of the 3,5,x-polymethoxy-l-alkanols series which areviscous liquids resembling glycerine and the low polyethylene glycols inconsistency. These materials are free from gum formation which is aserious drawback to the use of lubricants of the like of castor oil andderived compounds.

The presence in the hydraulic fluid of low boiling diluents either assolvents or decomposition products may result in vapor lock and is,therefore, to be avoided. The lowest member of the alcohol series is3-methoxy-butanol with a boiling point of 159 C. at 760 mm. The presenceof the higher members of the series increases the pot temperature atwhichsuch a mixture boils and may be varied depending on needs.

The wide solvent power of the 3,5,x-polymethoxy-1- alkanols makes itpossible to secure homogeneous solutions on mixing with commercialhydraulic fluids. The water tolerance of the 3,5,x-polymethoxy alkanolsis excellent.

The hygroscopicity of the 3,5,x-polymethoxy-l-alkanols is of a lowerorder than the glycols and polyethylene glycols in the same molecularweight range. Brake fluid mixtures containing these alkanols possessadvantages over materials containing the polyethylene glycols.

Inasmuch as mixtures of B-methoxy-l-alkanols and3,5,x-polymethoxy-l-alkanols may in themselves serve as hydraulic brakefluids because of their desirable properties, it is at times desirableto fit certain needs to incorporate auxiliary substances, such asanti-oxidants, corrosion inhibitors, viscosity modifiers, bufferingagents, and the like.

As anti-oxidants, there may be used any of the materials commonly usedto prevent the oxidation of oxidizable organic compounds, such asunsaturated hydrocarbons, e. g., rubber, unsaturated fuels, unsaturatedesters, such as oxidizable vegetable oil, ethers, vinyl compounds, etc.Examples of these anti-oxidants are para-tertiary butylg catechols,hydroquinones, and various morpholine derivatives, such asN-phenyl-morpholine, N-(p-hydroxyphenyl)morpholine, N,Ndiphenyl-p-phenylenediamine, diphenylamine, N phenyl-B-naphthylamine,p-phenylphenol, o-phenylphenol, di-p-methoxydiphenylarnine,mtoluylenediamine, various condensation products of aldehydes witharomatic amines: acetone-aniline and acetaldehyde aniline andbutylaldehyde-aniline, aldol-[S- naphthylamine, hydroquinone monobenzylether, and isopropoxydiphenylamine.

As corrosion inhibitors, we may use inorganic nitrites, such as sodiumnitrites, etc., organic nitrites, such as tertiary amine nitrites,chromates, such as sodium chromates and the like, inorganic boroncompounds, such as sodium tetraborate, organic boron compounds, such astriethanol amine borate and the like, certain sulfur compounds, such asdialkylthiourea, mercaptans, organic disulfides, diarylamine phosphates,such as diphenylamine phosphate, long chain alkyl sulfonamide acetatesodium salt, phosphites, such as sodium phosphite, organic phosphoricacid and organic derivatives of phosphorous acids, such asbenzene-phosphenic acid, etc.

In addition to the components named above, auxiliary substances, such asviscosity modifiers, bulfering agents, and coloring agents may beoptionally added.

As viscosity modifiers, there may be used various polyhydroxy compounds,such as glycol, glycerine, 1,2,4- butanetriol, 1,4-butanediol, propyleneglycol, etc., especially when used in conjunction with complex forminginorganic salts, such as borax, nickel and chromium salts, variouspolymeric materials, such as polyvinyl methyl ether, polyvinyl butylether, interpolymers of isobutyl vinyl ether and oleyl vinyl ether,various polyacrylates, such as polylauryl acrylate, polyolefines, suchas polyisobutylene or interpolymers thereof, etc.

As buffering agents, the following inorganic compounds are useful:borates, such as sodium tetraborate, sodium metaborate, ammonium andorganic borates, such as triethanolamine borates, sodium phosphite,tetraborate and the like, inorganic phosphate, such as the varioussodium phosphates, such as trisodium o-phosphate, disodium hydrogenphosphate, sodium pyrophosphate, organic phosphate, e. g.,triethanolamine phosphate, quinoline phosphate, salts of alkalinemetals, organic acids, such as sodium acetate, sodium citrate, sodiumbenzoate, potassium tartrate and the like, and mixtures thereof to yield(when admixed in the brake fluid composition) a pH above 7 and notexceeding a pH of 11.

In order to dissolve sodium borate in the hydraulic brake fluidcomposition, it was found advantageous to use a solubilizing agent, suchas ethylene glycol, in the formation. However, glycol is not essentialin the hydraulic brake fluid. This agent can be omitted in compositionsin which other buffers are incorporated. Also in place of ethyleneglycol in borax formations, other solubilizing agents, such as Carbitolcan be used.

The choice of coloring matter is not of critical importance in thefinishing of the hydraulic brake fluid provided it does not cause adeleterious effect on the viscosity of the fluid or exhibit corrosiveaction on the rubber or metal parts of the braking system. Mostdyestuffs are acceptable on these accounts since in most cases they areused only in minute quantities. Where coloring material or dyestuffs areadded for identification or other purposes, the sole requirement is thatthe dyestuff be sufficiently soluble in the hydraulic fluid. It has beenfound that dyestuffs of any class may be used. These include vatdyestuffs, diphenylamine derivatives, azo dyes, triphenylmethane dyes,and the like.

From the standpoint of rubber swelling, we have found that theproportions of 3-methoxy-l-butanol in the mixture must range from 20 to40% to yield good results. The 3-methoxy-1-butanol does not appear togive good results when employed alone or when incorporated with theforegoing auxiliary substances. The unusual and unexpected feature ofthe present invention is that the mixture, in addition to 20-40% of3=methoxy-1-butanol, must contain 60 to- 80% of' at least one of theindividual 3,5 ,x-polymethoxyl -alkanols-or a mixture thereof to yieldgood results. In these proportions the brake-fluid does not causeanyswelling or disintegration of rubber and completely eliminates-brakefailurethrough loss of fluid. Moreover, the blending of the individualalkanols of the mixture makes it readily possible to fit prescribedcommercial needs or requirements of certain brake fluids with respect tonon-volatility, viscosity, lubricity, and miscibility with auxiliarycomponents. For general all around good results particularly inautomotive hydraulic brake fluids, we.-have,foun d; that the; followingblend is ideal:

The following blend may also be used for all around good results:

Percent 3-methoxy-1-butanol 20-35 3,5-dimethoxy-1-hexanol 25-353,5,7-trimethoxy-l-octanol 10-25 3,5,7,9-tetramethoxy-1-decanol -203,5,7,9,11-pentamethoxy-1-dodecanol 2:5-10

Polymethoxy-l-alkanols. characterized by the following formula:-

wherein n represents an integer-of from 6'-to 8, 05-35%.

The higher polymethoxy alcohols of the type 3,5,7,'9',-11,13,xpolymethoxy-l-alkanols, i. e., wherein n in the above formulaequals 6or greater, maybe used in the range of 60 to:80%' to 20 to 40%of'3 methoxy-l'-butanol to yield a mixture which gives excellent resultswith respect to prevention of'rubber swelling. A mixture of 20% of3-methoxy-1-butanol and 80'% of 3,5-dimethoxyl-hexanol is comparableto-a mixture of 40% of- 3-methoxy-l-butanol and 60% of3,5-dimethoxy-1-hexanol. Both mixtures'possess suflicient lubricityunder operating conditions in various climatesandiextremesoftemperatures.

As illustrative of thepreparation of hydraulic brake fluids inaccordance withthe present invention, the following examples are given.The parts are by weight.

EXAMPLE I To 88.6 parts of amixture of3,5,x-polymethoxy alkanol(prepared in accordance with. Example3, United States Patent 2,618,663),containing byweight the following components:

Percent S-methoxy-l-butanol 35.0 3,5-dimethoxy-l hexanol 30.03,5,7-trimethoxy-l-octanol 22.0 3,5,7,9-tetramethoxy-l-decanol 7.53,5,7,9,11-pentamethoxy-l-dodecanol 3.6

Higher homologues characterized'by the above formula wherein n equals 6'or more 2.9

cps. and at +130 F.- was 7v cps. A.tube containing thismaterial wasmaintained at 40 F. for 6 days and at the endrofthis.period,.thetube.was tiltedfrom. a vertical to a horizontalposition. It was observed that flow began immediately. This compositionwas maintained at -60 F. for 6 hours. Flow began immediately upontilting. The: material: was; admixed: 1 0% by weight with waterandmaintained at--60 F. for 6 hours after which, it was clear anglfluid; The boiling point asdetermined by the temperature of, therefluxwas found to be, 345. E. Flash; point by-Cleveland opencup ASTMmethodwas 180 F. A sample of v the fluid was weighed into a ceramicboatand maintainedat: 210 F. for 48 hours in a location. free fromdrafts. Only 70% of thefluid evaporated. The pHgwas determined using aBeckmanpHmeter and found tobe: 9.3. A sample: was boiled under a refluxcondenser at its, atmospheric boiling pointof, abont345 F. for 8 hours.At'the conclusion of this treatment the material showed only a veryslight yellowing. No other evidence of decomposition was noted, and thesample was judged to be remarkably stable. This composition was admixedwith other-commercially available brake fluids, for example, a fluidcomposedof'about 35% by volume of ethylene oxide-propylene oxideinterpolymers, 32.5% by-volume of butyl Cellosolve and 32.5% by volumeof Carbito in addition to various inhibitors and found to be completelymiscible within the temperature range of--30to +60'F A 1% inchWagner-Lockheed FC666 wheel cylinder cup was measured to the nearestthousandth inch and introducedinto this composition at a temperature of158 F: for a' period of hours. Afterwards, the cup was againmeasured'and the increase in diameter due to the swelling eifects'of thecomposition was 0.018 inch. The above composition was brought in contactwith all the parts of a commercial wheel brake cylinder and maintainedat 158 F. for 14 days. Upon disassembly and examination, it'was foundthat the fluid caused no rust or corrosion. of; the-.metal parts andleft no hard, dry gummy residue or 'anysubstantial amount of sludge.Test strips, ofjtinned iron, cold rolled steel, aluminum, cast iron,brass: and copper; were bolted together so that the stripswere-inelectrical contact. These strips and a part of a: sampletakenfrom a Wagner-Lockheed FC666 rubber wheel cylinder cup; wereintroduced into the above composition, diluted, with 5% by volume ofdistilled water, maintainedfata temperature-of 210 F. for 120 hours.At.1the end of; this period the, strips were removed,disengagedandrpolished to remove corrosion products, if any. Corrosionlosses were observed by noting the weight lost (milligram per squarecm.)

Loss

Tin." 0 Steel 0. Brass 0 Copper milligram per sq. cm" 0.1 Aluminum 0Iron milligram per sq. cm 0.1

A lubrication test was carried out in a commercial hydraulic brake wheelcylinder actuated by a conventional mast cylinder driven by a cam. Theassembly was operated to simulate the actual actions of a brake innormal operation and the wheel cylinder was actuated in this fashionevery six seconds. The composition of Example I was introduced into thissystem and underwent 160,000 braking cycles at, the completion of whichthe moving parts were disassembled and examined for evidence of wear.Wearing was determined visually and by micrometer measurements. None ofthe surfaces exhibited as much as 0.001 inch wear.

EXAMPLE II To thesame solution of the composition of Example I therewere added20 parts per million'of a soluble copper phthalcyaninedyestuifThe performance data for this colored composition was substantiallyidentical with that asabove indicating that the colorant had nodeleterious effect. The presence of colorant is often desirable to aidin the detection of leaks in a hydraulic system.

EXAMPLE III To 99.5 parts of the mixed polymethoxyalkanol of thecomposition of Example I, there were added 0.4 part of coppernaphthenate and 0.1 part of triethanolamine. The mixture was stirreduntil a homogeneous solution resulted. This composition exhibited aviscosity of 420 cps. at a temperature of 40 C. and a viscosity of 16cps. at +25 C. When a Wagner-Lockheed FC666 wheel cylinder cup wasimmersed in this composition for a period of 24 hours at 158 F., the cupshowed, after an alcohol rinse and drying, a weight increase of only8.8%.

By way of comparison, B-butoxyethanol often used as a constituent incommercial brake fluid exhibited a rubber swell of 37.4%.

EXAMPLE IV A brake fluid composition was prepared by dissolvingone-tenth part of triethanolamine, 0.3 part of p-hydroxyphenylmorpholineand 0.1 part of the amine nitrite described in Example I, in 99.5 partsof a mixture of polymethoxyalkanols of Example I. The compounding wascarried out by stirring the constituents together at room temperatureuntil a homogeneous mixture resulted. When test strips of cast iron,steel, tin, iron, brass, copper and aluminum were immersed in thecomposition for a period of days at 100 C., it was found in all casesthat the weight loss of the strips due to corrosion was less than 0.3milligram per square centimeter. An average corrosion value of 0.5 mg.per sq. cm. over the above described test condition for these metals isnormally considered excellent.

EXAMPLE V A solution of 0.5 part of borax, 0.3 part of phenyl-B-naphthylamine, and .01 part of sodium nitrite in 25 parts of ethyleneglycol was added with stirring to 75 parts of the mixedpolymethoxyalkanols of Example I. The resul ing mixture was agitateduntil homogeneous. In a rubber swelling test in which a 1%. inchWagner-Lockheed FC666 wheel cylinder rubber cup was immersed in thiscomposition for 120 hours at 70 C., the diameter of increase of therubber cup was 0.018 inch. In a commercially marketed fluid consistingof essentially 65% nbutanol and 35 castor oil together with suitablestabilizers, the rubber swell in the same test was found to be 0.22inch.

EXAMPLE VI Polymetrzoxy alkanols obtained from polymethoxyacetals VinylEther to Methanol Ratio of Polymethoxyacetal 2.6:1 2.8:1 2.9:1 3.0:1

Component: Percent Percent Percent Percent 3-metn0x y-i-butanol. r 34. 327.8 23. 2 23. 8 3,5-dimethoxy-1-hexan0l 29. 7 28. 9 31. 2 27. 5 3,5,7-trimethoxy-l octanol 22. 2 24. 8 26. 4 21. 33,5,7,9-tetramethoxy-ldecanol 7. 5 12. 9 12. 1 18. 3 3,5,7,9,11-penta-1oxydodeeanol 3. 6 4. 3 4. 5 8. 0 3,5,7,9,11,13- and higher 2. 6 3.0 3. 03. 2

E EXAMPLE VII To each of the first set of four samples (which were setaside) each weighing about parts, there was added a. solution of 0.6part of borax, 0.35 part of phenyl-finaphthylamine, and 0.03 part ofsodium nitrite in 30 parts of ethylene glycol. The resulting fourmixtures were agitated until homogeneous. In rubber swelling tests inwhich a 1% inch Wagner-Lockheed FC666 wheel cylinder rubber cup wasimmersed in each of the four compositions for 120.hours at 70 C., thediameter of increase of the rubber cup was 0.012.

EXAMPLE VIII Example IV was repeated with the exception that 99.5 partsof the mixture of polymethoxyalkanols of Example I were replaced byparts of a mixture consisting of 40% of 3,5-dimethoxy-1-hexanol and 60%of 3,5,7,9,l1-pentamethoxy-l-dodecanol prepared in accordance withExamples 1 and 4 respectively, of U. S. P. 2,618,663. When thecompounded mixture was subjected to the corrosion strip test, the weightof loss of the strips due to corrosion was less than 3.3 milligrams percm.

EXAMPLE IX Example III was repeated with the exception that 99.5 partsof methoxyalkanols of the composition of Example I were replaced by 75parts of a mixture consisting of 20% of 3-methoxy-1-butanol and 80% of3,5,7-trimethoxy-1- octanol prepared in accordance with Examples 1 and 5respectively, of U. S. P. 2,618,663. When a Wagner- Lockheed FC666 wheelcylinder rubber cup was immersed in this composition for a period ofhours at 133 C.,

the cup showed, after an alcohol rinse and drying, a

wherein n represents an integer of from 6 to 10.

2. A hydraulic fluid composition consisting essentially of an alkalinebuffering agent selected from the class consisting of alkaline borates,phosphites, and phosphates, and a mixture of monoandpolymethoxy-l-alkanols consisting of 20 to 35% of S-methoxy-l-butanol,25 to 35% of 3,5-dimethoxy-1-hexanol, 10 to 25% of 3,5,7-trimethoxy-l-octanol, 5 to 20% of 3,5,7,9-tetramethox*- l-decanol, 2.5to 10% of 3,5,7,9,1l-pentamethoxy-ldodecanol, and 0.5 to 3.5% ofpolymethoxy-l-alkanols characterized by the following formula:

wherein n represents an integer of from 6 to 8.

3. A brake fluid composition consisting essentially of an alkalinebuffering agent selected from the class consisting of alkaline borates,phosphites, and phosphates, and a mixture of monoandpolymethoxy-l-alkanols consisting of 35.0% of 3-methoxy-1-butanol, 30.0%of 3,5-dimethoxy hexanol, 22.0% of 3,5,7-trimethoxy-l-octanol, 7.5% of3,5,7,9-tetramethoxy-l-decanol, 3.6% of 93,5,7,9,11-pentamethoxy-l-dodecanol, and 2.9% of polymethoxy-l-alkanolshaving the following formula:

wherein n represents an integer of from 6 to 8.

4. A brake fluid composition consisting essentially of an alkalinebufiering agent selected from the class consisting of alkaline borates,phosphites, and phosphates, and a mixture of monoandpolymethoxy-l-alkanols consisting of 20 to 40% of 3-rnethoXy-1butanol,25 to 35% of 3,5- dimethoxy-l-hexanol, 15 to 30% of 3,5,7-trimethoxy-1-octanol, 5 to 20% of 3,5,7,9-tetramethoxy-I-decanol, 2.5 to 10% of3,5,7,9,11-pentamethoxy-l-dodecanol, and 0.5

to 3.5% of polymethoxg l-alkanols characterized by the followingformula:

0113- CHCH2 CHz-0H [(IJCH: 11: wherein n represents an integer of from 6to 10.

References Cited in the file of this patent UNITED STATES PATENTS2,165,962 Mueller-Cunradi July 11, 1939 2,481,278 Ballard et al Sept. 6,1949 2,564,760 Hoaglin et a1 Aug. 21, 1951 2,564,761 Hoaglin et a1. Aug.21, 1951 2,618,663 Glickman et a1. Nov. 18, 1952

1. A HYDRAULIC FLUID COMPOSITION CONSISTING ESSENTIALLY OF AN ALKALINEBUFFERING AGENT SELECTED FROM THE CLASS CONSISTING OF ALKALINE BORATES,PHOSPHATES AND PHOSPHITES, AND A MIXTURE OF MONO- ANDPOLYMETHOXY-L-ALKANOLS CONSISTING OF 20 TO 40% OF 3-METHOXY-L-BUTANOLAND 60 TO 80% OF AT LEAST ONE 1-POLYMETHOXY-ALKANOL OF THE GROUPCONSISTING OF 3.5-DIMETHOXY-L-HEXANOL, 3,5,7,TRIMETHOXY-L-OCTANOL,3,5,7,9-TETRAMETHOXY-L-DECANOL, 3,5,7,9,11-PENTAMETHOXY-L-DODECANOL, ANDPOLYMETHOXY-LALKANOLS CHARACTERIZED BY THE FOLLOWING FORMULA: